Staphylococcus aureus belongs to the group of major contagious mastitis pathogens, whereas the coagulase-negative staphylococci (CNS) are also capable of causing opportunistic bovine mastitis. Many of these strains are resistant to penicillin or ampicillin because of the long-term use of beta-lactam antibiotics in agricultural and healthcare settings. Based on the simple and highly specific coagulase genotyping by PCR-RFLP used for discriminating among Staph. aureus strains, the relationship between phenotypic antibiogram and the polymorphism of coagulase gene was determined in this study. The staphylococci strains (835 Staph. aureus and 763 CNS) were isolated from 3,047 bovine mastitic milk samples from 153 dairy farms in 8 provinces from 1997 to 2004 in the Republic of Korea. Twenty-one (2.5%) Staph. aureus and 19 (2.4%) CNS strains were resistant to methicillin [oxacillin minimum inhibitory concentration (MIC) > or = 4 microg/mL]. The mecA gene was also found in 13 methicillin-resistant Staph. aureus (MRSA) and 12 methicillin-resistant CNS (MRCNS) isolates with a significantly higher detection rate of the mecA gene in MRSA with high MIC (> or = 16 microg/mL) compared with those with MIC < or = 8 microg/mL. Methicillin-resistant Staph. aureus and MRCNS were also more resistant to other antibiotics (ampicillin, cephalothin, kanamycin, and gentamicin) than methicillin-susceptible staphylococci. Among 10 different coa PCR-RFLP patterns (A to J) in 706 Staph. aureus strains, the main types were A (26.9%), B (17.0%), G (10.5%), and H (15.4%), with the frequent observation of the A and H types (6 and 10 isolates) in MRSA. This study indicates that major epidemic Staph. aureus clones may be spread between different dairy farms, and the profile of coa genotype can be applied for epidemiological investigations and control of bovine mastitis, particularly one caused by MRSA with specific prevalent coa types.

It is well-known that thermal treatment of aspartic acid produces poly(anhydr0aspartic acid) (polysuccinimide), which can then be hydrolyzed to sodium polyaspartate. Both polysuccinimide and sodium polyaspartate have been analyzed by a variety of one-and two-dimensional NMR techniques. 'H NMR indicates that sodium polyaspartate invariably contains a 3:l ratio of j3:a linkages, under a variety of synthesis and hydrolysis conditions. NMR and lW3C HMBC data show that the sequencing is random. Residual succinimide levels in sodium polyaspartate are detectable down to about 1% by lH NMR. COSY data of polysuccinimide and lW16N HMQC-TOCSY of polysuccinimide synthesized from 100% 15N monomer indicate that phosphoric acid catalysis produces linear polymers, while uncatalyzed materials are branched.

enantiomeric selectivity occurs as well with cleavage. With A-R u ( T M P )~~+ , twice the cleavage efficiency of the A-form polymer is observed in comparison with A-Ru(TMP)~*+.In summary, A-Ru(TMP);+ has been shown to bind selectively to A-form polynucleotides and in the presence of light to cleave A-form polymers. This chiral probe should be useful to investigate DNA conformational heterogeneity in mapping sites in the A conformation along the helical strand. The role played by DNA secondary structures in protein recognition and in the expression of genetic information may be better understood by using this and other chiral complexes which are targeted specifically to different conformations.(20) Cadet, J.; Teoule, R.

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The sequences of the ccrAB genes from bovine-, canine- and chicken-originating methicillin-resistant Staphylococcus (S.) epidermidis (MRSE) and bovine methicillin-resistant Staphylococcus (S.) aureus (MRSA) were compared to investigate the frequency of intra-species horizontal transfer of the staphylococcal cassette chromosome mec (SCCmec) complex. Nineteen MRSE strains were isolated from bovine milk, chickens, and dogs, and their genetic characteristics were investigated by multilocus sequence typing and SCCmec typing. Among the animal MRSE strains, the most frequent SCCmec type was type IV, which consisted of the type B mec complex and ccrAB type 2. The ccrA2 and ccrB2 genes were sequenced from the bovine, chicken and canine MRSE strains and compared with those of the bovine MRSA strains. The sequences generally clustered as MRSA and MRSE groups, regardless of the animal source. Additionally, no bovine MRSE sequence was associated with the bovine MRSA groups. Although most of the bovine MRSE and MRSA isolates possessed SCCmec type IV sequences, our results suggest that the intra-species gene transfer of the SCCmec complex between bovine S. aureus and bovine S. epidermidis strains is not a frequent event.